interesting "chalk test" results

kayadog · **Posted:** Mon Oct 22, 2007 4:12 pm

I did the chalk test to see what PSI I should run on my 245/70r16 Grabber AT2's on 16x8 Cragars on an otherwise stock 05 sport.

The best results were:

36 PSI front
32 PSI rear

tommudd · **Posted:** Mon Oct 22, 2007 5:32 pm

That sounds about right, takes a while to do it but it helps a lot with wear

Tom

TheJawsOfDeath · **Joined:** Sun Nov 05, 2006 3:56 am **Posts:** 305

..and a chalk test is....??

tommudd · **Posted:** Thu Oct 25, 2007 9:00 pm

go to a nice big parking lot, take chaulk and make a mark across each tire drive a short distance and see how it wore off, if in the center too much air, on the outside too little, best way is to pump them up real good and then you can keep letting air out until the chaulk mark is all gone after a short straight drive, you dont have to go very far at all for the chaulk to come off. may have to rechaulk several times and keep lowering the pressure but it works

help or confuse you? My wife is the teacher, I know what I mean even if no one else does :wink:

tom

kayadog · **Posted:** Fri Oct 26, 2007 7:57 am

Perfect description. It really helped me find the "sweet spot" for my new tires. They are quiet and handle nicely. Hopefully it will contribute to longer wear too.

I think this test would show if your Jeep need an alignment too if the chalk only stayed on one edge.

Jeepman56 · **Posted:** Fri Oct 26, 2007 10:02 am

I have the 245/70 10 at2s but on stock rims. Would the psi suggested above be the same for me?

kayadog · **Posted:** Fri Oct 26, 2007 10:31 am

I doubt it because the wider rim will change the contact patch and the weight distribution of the tires. The wider wheel offset probably changes the weight distibution too.

The only way to really know is to do the chalk test. It is really easy. I used regular chalkboard chalk and did it in front of my house in 20 minutes. I ended up changing my PSI significantly enough to probably make a difference in fuel economy and tread wear.

Make sure you load your Jeep like you normally would for it to work.

Pote · **Posted:** Fri Oct 26, 2007 12:41 pm

awesome. My 3 and 4 year old kids did my chalk test for me. I came home one afternoon and the entire driveway was like a Davinci masterpiece of chalk artwork...ok maybe not davinci, more like a Pollock painting, but driving into the driveway put a multi-colored chalk ring around all four tires completely around the tire. I took that as a sign to test it and drove around the circle driveway onto the street and did my test. thanks kids!!!! oh yeah, sorry about ruining your artwork on the drive!! LOL :lol:

dgeist · **Posted:** Fri Oct 26, 2007 12:50 pm

Jeepman56 wrote:

I have the 245/70 10 at2s but on stock rims. Would the psi suggested above be the same for me?

If you do the test, please post back. I'm planning on getting that size on my stock rims and it'd save me some time

P.S. has anyone run a different pressure front/rear and had their TPS system not complain? Mine gets mad if any tire it more than 2 PSI off from the others but I haven't tried it with a pair of them.

Pote · **Posted:** Fri Oct 26, 2007 1:01 pm

dgeist wrote:

Jeepman56 wrote:

I have the 245/70 10 at2s but on stock rims. Would the psi suggested above be the same for me?

If you do the test, please post back. I'm planning on getting that size on my stock rims and it'd save me some time

P.S. has anyone run a different pressure front/rear and had their TPS system not complain? Mine gets mad if any tire it more than 2 PSI off from the others but I haven't tried it with a pair of them.

with my 245's on stock rims, they all like 35 psi all the way around.

Jeepman56 · **Posted:** Fri Oct 26, 2007 4:18 pm

Thanks Pote, saved me a little time, although another reason to mess around with the Jeep is always good too.

DryBones · **Posted:** Fri Oct 26, 2007 4:58 pm

I've been trying this for an hour and nothing happens? Do you think it could be all the rain????? :lol:

Pote · **Posted:** Fri Oct 26, 2007 5:13 pm

DryBones wrote:

I've been trying this for an hour and nothing happens? Do you think it could be all the rain????? :lol:

remember, chalk and NOT a black sharpie!

Pote · **Posted:** Fri Oct 26, 2007 5:15 pm

Jeepman56 wrote:

Thanks Pote, saved me a little time, although another reason to mess around with the Jeep is always good too.

and you can color your drive like my kids did...great fun.

interesting "chalk test" results

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